While on holiday I noticed some specks on the inside mirror of my D40. I stupidly tried to wipe these clean using some lens cleaning paper, and somehow the mirror/internals became (what looks like) scratched.

I'm really annoyed obviously, and though this doesn't affect the pictures taken at all it does show up in the viewfinder clearly. As it doesn't affect the photographs it is by no means a disaster, but I'm wondering

a) what the approximate cost of getting this fixed, if its at all possible, is

b) if somehow I can sneakily use the Nikon warranty to get it corrected for free

Obviously the best way to answer these questions is to take my D40 into a camera shop here in Japan, but I wanted to see what others thought my best bets were.

Seems like it's very easy to do more harm than good in the world of DSLRs, I have a similar problem. I tried to blow dust off my sensor but I blew more on to it instead.

Could it be that you've smeared the dirt on the mirror and not scratched it? I know Nikon Malaysia cleans for free for the duration of the camera's warranty, same in Singapore I think, not sure about elsewhere.

Maybe your focusing screen is scratched? They're supposed to be quite delicate from what I've heard. I think you can replace them for not too much.

Thanks for your advice Graham. I'm fairly certain its stratched, and I'm really annoyed as I don't see how I could possibly have done this with lens cleaning paper. It's the upper mirror that's stratched not the lower one- not sure if this helps with diagnosis.

I'll take it and my warranty to a camera shop and hope for the best, although I'm fairly sure I'll have to pay to replace it.

I would recommend the Giotto Rocket blowers to assist in cleaning rather than a blower brush. They're more effective and being non-contact, my 1st choice to clean my sensors. If that doesn't work, then depending on severity, it's either clone tool or taking it in for servicing.

I'm inclined to give it to a professional to do. Martin at Martin's Camera Shop has had professional photographers come in and says "this doesn't work" – the don’t RTFM. He sends it to these guys at fixation (http://tinyurl.com/23a3yw) and one of the technicians has spent 30 years at Canon and now is employed by fixation. Martin said there is nothing he doesn’t know about Canon equipment. The guy at fixation will say there is nothing wrong with this camera; they need to check this setting and so forth.

The cleaning process is a delicate matter, so change your lenses in an area were dust etc is not whirling around. A good place is a car.

The first time you clean your sensor you are an amateur and you risk damaging the sensor and de-calibrating the mirror. These guys will clean the sensor until it is dust free and check the calibration of the mirror and anything else that may concern you.

You can go there, pay your £49.75 and it will be done in 25 to 35 mins.

If you clean the sensor yourself, you must use high-quality fluid; swabs and brushes so why not just pay the money and let a pro do it.

Look after your camera but let the pros mess around with the guts of it.

I’m an IT engineer and network engineer and I have had clients spend days trying to fix a problem because they thought they could do it. I get it and fix in with a couple of clicks. They are amazed and say how did you do that and how is it you know so much. Why because this is my job. It’s flattening being called a genius too.

I don’t fix cars because I don’t know anything about them so I would go to a reputable mechanic.

A little knowledge can be a dangerous and expensive thing. Be smart and seek out a pro.

a little bit straying but if you do leave these dust particles on the sensor and leave the cameras auto sensor to sort it out, will whatever is the makeup of the dust possibly eat into the sensor itself and shorten the life span or worse still will it do it at the time of your shot of your life moment.
One of the cameras I use is the Canon 400d and even though I only use two lenses on it for specific shot and dont change around that much I still have gathered 3 fairly biggish dust spot which the auto cleaner wont remove.
So to manually clean or not seems to be the question.

Do they make sensor cleaners for the 400d seeing that it is meant to be "Self Cleaning"

self cleaning doesn't work that great, and it wont eat into the sensor because the sensor is covered by the auto cleaning thing. So if it is something corrosive it won't actually be eating into your sensor.

I've been told manufacturers like Nikon are usually very forthcoming with repairs, even if it is due to your own fault that damage has occured. My advice is to talk about this at the store where you bought your camera (or any store if you bouht online) and ask them what your chances are...